1. Field of the Invention
The present invention relates to an airbag designed to protect the occupants of a vehicle during a collision. More specifically, the invention relates to a folded rigid knee airbag that prevents the lower body portion of a vehicle occupant from being propelled forward during a collision.
2. Description of Related Art
Inflatable airbags enjoy widespread acceptance as passenger restraints for use in motor vehicles. In fact, vehicle manufacturers are now required to install airbags in most new vehicles manufactured for sale in the United States.
Airbags are often installed in the steering wheel and in the dashboard on the passenger side of a car. These airbags are typically covered by a trim cover panel that is made of rigid plastic, and that is configured to be opened by the pressure created by the deploying airbag. These airbags are typically used for the primary deceleration of a vehicle occupant since, in a large fraction of collisions, the occupant is accelerated forward toward the windshield. Thus, such an airbag will be referred to herein as a “primary airbag.”
A primary airbag is typically in communication with an inflator, which is typically in communication with a sensor mechanism configured to sense an impact to the vehicle. Upon receipt of an electrical signal transmitted from the sensor mechanism, the inflator discharges, causing the primary airbag to inflate. In its inflated position, the primary airbag prevents the upper body portion of a vehicle occupant from being propelled forward toward the windshield. When this occurs, there is a tendency for the lower body portion of the occupant to be propelled forward and under the primary airbag. This tendency is referred to as “submarining,” and may be quite pronounced when the occupant is not properly restrained by a seat belt.
Knee airbags have been developed in order to prevent submarining. Knee airbags deploy during a collision event and engage an occupant's knees or lower legs, thus holding the occupant in place on the seat and preventing submarining.
One known rigid knee airbag is a metallic bladder which includes two metal sheets that are welded together along the edges. However, during deployment the center of such a metallic bladder expands to a greater extent than the peripheral regions. Therefore, the surface of such a metallic bladder can interact with a vehicle occupant at an angle during an accident.
Another known rigid knee airbag is an inflatable bladder that includes a forward main panel and a rearward main panel. Each of the main panels has a generally octagonal shape prior to inflation. The inflatable bladder also includes right and left end panels. Prior to inflation, the end panels are folded to form pleat folds. However, such a knee airbag has a projected area prior to deployment which is much larger than the ultimate reaction surface presented to the occupant. Such an airbag is therefore inefficient to package inside a vehicle.
Accordingly, it would be an advancement in the art to provide a folded rigid knee airbag with a front panel that remains substantially flat during inflation. It would be a further advancement in the art to provide a folded rigid knee airbag wherein the cross-sectional area of the airbag in its inflated configuration is substantially equal to the cross-sectional area of the airbag in its compact configuration. The present invention provides these advancements in a novel and useful way.